Heater heads for hot gas engines must offer a predetermined resistance against inner flow of working gas and they must be arranged in such a way relative each other that they offer a predetermined resistance against a flow of combustion gas between them, the arrangement being such that the temperature of the heater head may be constant and uniform all along the heater head and at all loads of the hot gas engine.
Hitherto this has been obtained by using a great number of pipes of different length and shape or it has been necessary to use manifolds extending into central parts of the heater head requiring extra shields or pipe bends as protection against overheating.
Example of prior art literature: U.S. Pat. No. 2,817,950.
This invention relates to a hot gas engine heater head of the kind (herein called "the kind defined") comprising heater pipes in an annular disposition around a central axis for heating by common combustion means, the heater pipes connecting cylinder tops to respective regenerator housings.
A heater head of the kind defined should fulfil several requirements. One of these requirements is simplicity in manufacture; another is proper resistance against the working gas flow within the heater pipes as well as against the flow of combustion gases between the heater pipes.
According to the present invention a hot gas engine heater head of the kind defined is characterised in that each heater pipe has a curved portion of a shape which corresponds substantially to the shape of an involute curve upon a conical surface, the curved portions of the heater pipes being disposed uniformly and equi-spaced side-by-side.
In an advantageous construction each heater pipe has a substantially straight portion which extends substantially parallel to the said central axis.
For convenience the straight portions of the heater pipes extend along a right-cylindrical surface of which the axis coincides with the central axis.
For economy in manufacture the heater pipes may be all similar to one another.
In a preferred arrangement the curved portions of the heater pipes are connected through manifolds to the respective regenerator housings, and the manifolds to the regenerator housings substantially constitute a ring centred upon the central axis, and the substantially straight portion of the heater pipes are connected through manifolds to the respective cylinder tops, and the manifolds to the cylinder tops substantially constitute a ring centred upon the said central axis.